1. Field of the Invention
The present invention relates to a time-division switch and a time-division switching method for a time-division switch.
2. Description of the Related Art
Conventionally, a time-division switch merely has a basic function to arrange time slots of a data highway inputted thereto arbitrarily on time slots on another highway to be outputted to interconnect different apparatus, which are physically connected to each other outside the time-division switch, with such time slots so that data or an audio signal may be communicated between the different apparatus.
Meanwhile, such functions as sending out a tone signal of a busy-back tone, or the like or sending out or receiving a multi-frame signal must all rely upon externally connected apparatus for exclusive use.
Consequently, it cannot be avoided that the system is discretized and exhibits a large scale.
As described above, a conventional time-division switch requires use of external apparatus for exclusive use for almost all required functions other than the switching function of time slots.
For example, the PIAFS (PHS Internal Access Forum Standard), which is a data transfer protocol of the PHS (Personal Handyphone System), can be compared to a 640-bit multi-frame signal train. If it is tried to use the PIAFS protocol for processing of a plurality of lines, then a time-division switch for line separation for distinguishing an audio signal and data from each other, a function of producing multi-frames of 640 bits specified by the PIAFS and inserting the multi-frames into suitable time slots and another function of dropping a multi-frame signal train and extracting a data train of 640 bits from the multi-frame signal train are required.
More particularly, for communication of an audio signal, only switch connection is required. However, for communication of data, connection to an apparatus for exclusive use is required even for a call of a same time slot as in the case of the data transfer protocol described hereinabove because contents of the signal are different, and the apparatus for exclusive use must have functions different from mere switch connection such as functions of extracting a multi-frame signal train of 640 bits mentioned hereinabove, performing protocol control specified by the PIAFS based on the signal train and securing the normality of the data.
Further, as the number of lines increases, also the numbers of required apparatus for exclusive use increase, which increases the scale of the system.
Furthermore, if also such apparatus as an apparatus for sending out guidance information such as a busy-back tone mentioned hereinabove are included, also the number of types of apparatus for exclusive use increases, and as the number of service functions of the system increases, also the number of apparatus for exclusive use is inclined to increase while they are discretized for different functions.
It is an object of the present invention to provide a time-division switching method which allows a time-division switch to have several functions which are conventionally achieved by different apparatus for exclusive use.
It is another object of the present invention to provide a time-division switch which achieves several functions which are conventionally achieved by different apparatus for exclusive use.
Where principal basic functions required by such apparatus for exclusive use as described above are examined, it is considered that, for a tone signal, data of a time slot of any highway repetitively appear with a certain periodicity. This also applies to an audio guidance. Meanwhile, in the PIAFS protocol described above, multi-frames of 640 bits repetitively appear. Thus, generally speaking, basic functions of almost all apparatus for exclusive use can be included in signal processing of multi-frames having a certain periodicity.
Taking notice of the foregoing, the present invention provides a method wherein a time-division switch is provided with, in addition to a switching function wherein time slots of an arbitrary highway inputted are transferred and placed into time slots of another arbitrary highway to be outputted, a reading/writing function for an external memory and the external memory is controlled as an imaginary time slot, thereby providing data insertion and data dropping functions. The time-division switch further has a controlling method wherein read and write addresses of the external memory are circulated so that apparatus for exclusive use in the prior art can be replaced with imaginary time slots to realize economization and miniaturization.
In particular, in order to attain the objects described above, according to an aspect of the present invention, there is provided a time-division switching method for switchably connecting time slots between different highways in time-division multiplex communication, comprising the steps of temporarily storing time slots on any of the highways for each time slot, designating time slots on any of the highways and designating phase conversion arrangement, producing an additional new time slot, calculating external memory read address designation bits for reading out data from an external memory from a head address, an end address and an address counter, performing at least one of updating insertion wherein setting data read out in accordance with the external memory read address designation bits is inserted into a pertaining time slot to update the time slot and new insertion wherein the setting data is inserted into the new time slot, and dropping data from the temporarily stored time slots of the highway in accordance with data drop designation bits and storing the dropped data into the external memory in accordance with the external memory storage address designation bits.
According to another aspect of the present invention, there is provided a time-division switch with an inserter and a dropper of an external memory added type for switchably connecting time slots between different highways in time-division multiplex communication, comprising a time slot memory for temporarily storing time slots on any of the highways for each time slot, phase conversion arrangement means for designating time slots on any of the highways and designating phase conversion arrangement, additional time slot production means for producing an additional new time slot, address calculation means for calculating external memory read address designation bits for reading out data from an external memory from a head address, an end address and an address counter, insertion means for performing at least one of updating insertion wherein setting data read out in accordance with the external memory read address designation bits is inserted into a pertaining time slot to update the time slot and new insertion wherein the setting data is inserted into the new time slot, and dropping means for dropping data from the temporarily stored time slots of the highway in accordance with data drop designation bits and storing the dropped data into the external memory in accordance with the external memory storage address designation bits.
In the time-division switching method and the time-division switch, external data read out in accordance with the external memory read address designation bits may be temporarily stored into an external data storage memory.
The time slot to be newly inserted may be a time slot of a multi-frame of a signal train of a number of bits equal to an integral number of times a number of bits which compose a time slot.
The setting data to be inserted may be a tone signal.
With the time-division switching method and the time-division switch, three address factor storage areas for a head address, an end address and an address count are provided for each time slot, and circulating designation of address is possible for each time slot. Consequently, the time-division switch can perform supervision or sending out of a multi-frame signal for all time slots and can also perform an ordinary switching function. Accordingly, not only communication of audio data, but also transfer of data having a nature of a multi-frame signal train as specified in the PIAFS can be performed collectively by a single LSI without using an external apparatus for exclusive use. Consequently, the time-division switch can perform communication of both of data and an audio signal and can be implemented in such a small size and low power consumption that it can be well applied to a system construction for mobile computing and so forth.
The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings.